In order to manufacture high quality toffee, it is necessary to evaporate water from the ingredient mix continually during the cooking process in order to obtain a fine flavour and consistency in the finished product. In addition, as the ingredients contain a high proportion of sticky milk proteins, which are highly susceptible to burning, it is necessary to agitate the mix continually during cooking in order to prevent it from sticking to the heat transfer surfaces of the vessel and burning. Such agitation is also necessary to produce a fine mix of the ingredients.
While traditionally toffee was manufactured by boiling the toffee ingredients in batches in open vessels, such a method does not lend itself to mass production. Various apparatus are known for the manufacture of toffee by a continuous process.
For example, in EP-A-0 061 232 is disclosed an evaporation apparatus for use in the cooking of toffee wherein a heated closed vessel is continuously fed with an ingredient mix via the base of the vessel and the cooked mix is permitted to overflow over a weir out of the top of the vessel. Rotating paddles within the vessel swirl the ingredient mix into a vortex in order to prevent it sticking to the interior of the vessel. The extremities of the vortex are also urged towards the weir to exit the vessel.
In contrast, in the use of chocolate in the production of confectionery items, it is necessary to temper the molten chocolate mix in order to prevent fat bloom from occurring in the finished product and to give a good appearance to the finished item. Fat bloom is likely to occur when chocolate has been poorly mixed and solidified during production. Tempering of the chocolate is, therefore, carried out to mix the ingredients thoroughly and to control the crystallization of the various fats within the mix. Such tempering is generally achieved by heating the chocolate to melt all fat crystals therein and thereafter controlling its cooling, whilst at the same time stirring or agitating it, so that stable fat crystals are only slowly formed therein.
It is, however, again convenient if chocolate tempering can be carried out as a continuous process within a confectionery manufacturing process as a whole.